Cision CEO Peter Granat has resigned after a Chicago investment firm gained control of the PR software company in May. He takes the reins of the combined Vocus-Cision.

GTCR Investment, which acquired rival Vocus earlier this year, has reshaped Cision's board and moved to delist its shares from the Nasdaq OMX Stockholm exchange since gaining control of more than 71% of the company.

Granat took the CEO reins in 2012 after serving as European head. He joined the company in 2003 on its acquisition of MediaMap.

Magnus Thell, current head of Cision Europe, was named interim president and CEO.